I gotta go with Mupps on this one. Synergy is very real, and honestly a very good example of how amazingly sensitive our ears are to change. While they may not seem like much, electronic/electrical components are typically produced with very VERY low fault tolerance, which means that unless something went amiss, one amp should sound the same no matter how many times it is produced (I'll stick with solid state for now, because tubes are outliers in this). If you change, say, the Opamps in it to a different model, the amount of microcomponents in that one little chip have changed quite a bit.
On to the point: Mupps hit it on the head when she said that ideally all of our upstream would simply be a wire with gain. Hypothetically, this would be ideal right? Not so. While coloration is technically a flaw in what we are trying to achieve, the FR of any sound producing device (speaker, headphone, IEM) may sound flawed to our ears, despite them measuring perfectly. Mental and physical differences are the variables. Your brain may enjoy a dip in the 1K region. Your ears, while there is a range where they commonly resonate, may have a different resonant peak from the person down the road. A good example of these points is the Etymotic ER4S. It measures splendidly on paper, but some people find it painful to listen to, while others simply find it boring, while even more may find it to be the closest they've ever been to truly feeling their music. The O2 is another great example. It measures [supposedly] fantastic on paper, but that flat sound isn't what many MANY people enjoy on their gear. While researching them a bit, I read just as many people hate the O2 sound as they do love it.
So what does this have to do with the point of synergy?
Synergy in our hobby, to me, is the personal quest of making two inherently flawed devices find their mate. That is where I feel not only the term works without causing wars in the community, but also is price free. This quest is harder for some people than others, and sometimes that sound tweak for the IEMs you love so much may be a $1K superDAP, or hey, it may be a yard sale Ipod Shuffle that makes them sound the best you have ever heard. Amps do fulfill a need of providing adequate current and voltage, but it is also another method we use to alter what we are hearing. The UHA-6 MKII was well loved by many (and many around the diary too), and the main word I heard about the amp was "transparent". To me, that says "hey, I have this setup sounding exactly how I want it to, now to add the muscle behind it". Some pieces are overall very balanced and can accept many different headphones to make people smile (DX100 comes to mind), but others are colored in sound, and it isn't a flaw either. The PA2v2 comes to mind.
TL;DR: Synergy is real, but you have to find what makes it work besides throwing money at the problem.
EDIT: Apparently did something strange last night, wake up and there's a big crack in the middle of my phone's screen. Eff.
Edited by mosshorn - 5/19/13 at 9:44am